On-chip collimated planar ‘Free Space’ Gaussian beams utilising optical lenses on a silicon on insulator chip

Several important applications in integrated photonics such as sensors, on-chip optical microscopes, microwave channelizers, and even optical interconnects between chips are implemented using planar `free-space´ optics. These do require formation and reception of well collimated Gaussian beams in free space. The conventional way to launch the collimated beam is to use free space optical lenses. However, it is very difficult to couple a collimated Gaussian beam into an optical chip while still maintaining beam collimation in free space. Therefore, the on-chip approach is preferable. In this work, a TE Gaussian beam from a PM fibre is launched into the focal spot of biconcave lens through grating coupler. After passing through the biconcave lens, the collimated beam will propagate in the free space, which is shown in Fig.1(a). The biconcave lens was composed of two semi-disks with radius of 100μm.